Problem: Sometimes brick process is getting crashed at the time of stop brick while brick mux is enabled. Solution: Brick process was getting crashed because of rpc connection was not cleaning properly while brick mux is enabled.In this patch after sending GF_EVENT_CLEANUP notification to xlator(server) waits for all rpc client connection destroy for specific xlator.Once rpc connections are destroyed in server_rpc_notify for all associated client for that brick then call xlator_mem_cleanup for for brick xlator as well as all child xlators.To avoid races at the time of cleanup introduce two new flags at each xlator cleanup_starting, call_cleanup. BUG: 1544090 Signed-off-by: Mohit Agrawal <moagrawa@redhat.com> Note: Run all test-cases in separate build (https://review.gluster.org/#/c/19700/) with same patch after enable brick mux forcefully, all test cases are passed. Change-Id: Ic4ab9c128df282d146cf1135640281fcb31997bf updates: bz#1544090